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I have recently started working at an academic publisher on their digital products. In this industry it's standard practice to use link resolvers - such as SFX from ExLibris - when updating a product as an easy way to manage URL migration. However, these link resolvers appear to use 302 redirects which makes me concerned about the potential for rankings to drop. Does anybody out there know about the use of link resolvers and their effects on search engine visibility? The main sources of information I've been able to find so far have been a Google Webmaster Central forum post and a piece on DOI news from 2005. Any information that's more up to date would be very useful, thanks!

Background: A company I am working with recently consolidated content from several existing domains into one new domain. Each of the old domains focused on a vertical and each had a number of product pages and a number of blog pages; these are now in directories on the new domain. For example, what was www.verticaldomainone.com/products/productname is now www.newdomain.com/verticalone/products/product name and the blog posts have moved from www.verticaldomaintwo.com/blog/blogpost to www.newdomain.com/verticaltwo/blog/blogpost. Many of those pages used to rank in the SERPs but they now do not. Investigation so far: Looking at Search Console's crawl stats most of the product pages and blog posts do not appear to be being indexed. This is confirmed by using the site: search modifier, which only returns a couple of products and a couple of blog posts in each vertical. Those pages are not the same as the pages with backlinks pointing directly at them. I've investigated the obvious points without success so far: There are a couple of issues with 301s that I am working with them to rectify but I have checked all pages on the old site and most redirects are in place and working There is currently no HTML or XML sitemap for the new site (this will be put in place soon) but I don't think this is an issue since a few products are being indexed and appearing in SERPs Search Console is returning no crawl errors, manual penalties, or anything else adverse Every product page is linked to from the /course page for the relevant vertical through a followed link. None of the pages have a noindex tag on them and the robots.txt allows all crawlers to access all pages One thing to note is that the site is build using react.js, so all content is within app.js. However this does not appear to affect pages higher up the navigation trees like the /vertical/products pages or the home page. So the question is: "Why might product and blog pages not be indexed on the new domain when they were previously and what can I do about it?"